Polishing-block



H. M. HOFFMAN.

POLISHING BLOCK.

APPLICATION FILED JULY l. I9I5.

1,332,896. Patented Mar. 9, 1920.

jf y f' Arronnlvl.'

UNITED sTATEs PATENT oEEIcE.

HOHER M. HOFFMAN, F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TOl PITTSBURGH PLATE GLASS COMPANY, 0F PITTSBURGH, PENNSYLVANIA, A CORPORATION 0F PENNSYLVANIA.

POLISHING-BLOCK.

Specification of Letters Patent.

Patented rMar. 9, 1920.

Application led July 17, 1915. Serial No. 40,348.

' To all whom t may concern.'

rougeis used are expensive` and under the:

present practice are removed when about alf worn through to avoid, any danger of the pads tearing during the polishing opf eration and thus permitting the metal of the runner blocks on which the pads are carried to engage the glass land scratch it. My improvement ,permits the felts to be almost entirely worn through without any danger of scratching the glass. Certain embodiments of the invention are illustrated in the accompanying drawings, wherein- Figure 1 is a vertical section through a polishing blockembodying my invention, Fig. 2 is a bottomv plan View of the polishing block of Fig. 1, and Figs. 3. and 4 are vertical sections through the lower portions of modified forms of blocks.

Referring to Figs. land 2 1 is a metal runner block; 2 is the framework from which the block is supported over the grinding table; l3 is the spindle by means of which the blockv is mounted for universal movement in order to adjust itself to the surface of the glass over which the block is moved; 4 is a clamp provided with bolts 5 for securing the block to the spindle; 6 is a sheetor pad of felt held in position by means of the clamping ring '7 and 8 is a polishing felt cemented to the lower surface of the sheet 6. It will be understood that the block as just described is one of a large number, usually arranged yin three sets, and mounted over the ordinary grinding table, the blocks being free to rotate, and their rotation being caused by the rotation of the grinding table carrying the glass sheet.

Aside from the additional polishing felt 8 as above described the block is precisely the same as heretofore used in the art, the rouge being applied to the felt 6 and 'such felt constituting the oli'shing element instead of the felt 8. his arrangement involved a considerable waste of felt as it was necessary to replace the felt 6, when it was about half worn through in order to avoid any danger of the felt tearin and the iron 1 coming in contact with t e glass and scratching it. Furthermore the bending ofthe felt at the edges of the block 1 caused undue wearing at these oints, the felt being about of an inch thick and relatively sti The use of the felt 8 cemented to the bottom of the other felt greatly increases the economy in the use of the felt since the felt8 7 can be worn almost through before it becomes necessary to replaceit. The impervious rubber cement which is referably employed sinks into the felt, a s ight distance, not over of an inch,y and it is necessary to remove the felt when worn down to this layer of cement, but the waste involved is obviously relatively slight as compared with that of the -old procedure. Another advantage incident'to this construction liesin the fact that scrap felt may be employed in making up the pad 8, Fig. 2 illustrating how corner sections can be utilized for this purpose. This use of built-up felts was of course not possible with the arrangement as heretofore employed wherein athe felt was held only at its edges by the ring 7 The felt 8 also wears uniformly since it is perfectly at and there are no corner portions tending to bulge down as was the casewith the felt as heretoforev used. Since the pad 6 is not used for polishing purposes, some other, and less expensive fabrlc may be used, if desired.

Fig. 3 illustrates a modification in which 1 is the metal runnerblock, 6 is a backing pad secured to the runner block, and 8 is a polishing felt cemented to the lower sideof the pad 6. The pad 6 may be secured to the block 1 by ,means of cement or in any other manner and the composition of such pad may be either felt or any other yielding material. The cement between the sheets 8 and 8 is indicated by the heavy lines 9 which extend inward from the edge a relatively short distance. The central portion of the felt 8 is preferably not cemented to the pad 6 as it is desirable to have the' major portion of the felt more or less free to yield laterally somewhat. This yielding is permitted in the construction of Fig. l by reason of the fact that the felt 6 is supported only at its edges.

' Fig. 4 illustrates still another modification in which l is the runner block, 6 is the yielding hacking pad, and 8" is the polishing felt. The backing pad 6 is in this instance made of a rubber composition held in place by screws 10. To add to the security the pad may also be vulcanizedor cemented to the lower side of the block l". The felt 8 is secured to the lower side of the pad 6 by means of cement applied either at-the edges as in the construction of Fig. 3 or over the entire upper surface of the felt. Various other arrangements might obviously be employed for carrying out the invention, 'but the foregoing will be sufficient to illustrate the principle of construction inyolved and the breadth of the invention.

What I claim is:

l. In combination, a plate glass polishing block comprising a metal runner block, a

pad of yielding material secured on the lower surface of the runner block7 and a disk of polishing felt cemented to the lower surface of the pad. and lying throughout in a horizontal position.

2. In combination, a plate glass polishing block comprising a metal runner block, a sheet of polishing felt mounted on the lower surface of the runner block with its edge turned up along the sides of the block, clamping means for securing the turned up edge to the block, and a sheet of polishing kfelt cemented to the lower surface of the first sheet, and lying flat throughout its area and in a horizontal position.

3. In combination, a plate glass polishing block comprising a supporting block, a pad ot' yielding material secured on the lower side of the supporting block, and a sheet of polishing felt having its upper surface cemented over substantially itsentire area to the pad of yielding material, and the entire sheet of felt lying inv a horizontal position from the center to the extreme edge of the sheet. y

HOMER M. HOFFMAN. 

